German Published Patent Application No. 40 04 110, which is not prior art with respect to the present application, discloses a method and a device for controlling a diesel or gasoline engine using a solenoid-valve-controlled fuel-metering system. The fuel pump comprises a pump piston, which is driven by the camshaft and which pressurizes the fuel and delivers it into the individual cylinders. The beginning and end of fuel delivery are established by means of at least one solenoid valve. For this purpose, a control unit calculates trigger instants for the solenoid valve dependent upon markings located on a shaft.
In such systems, the problem arises that the control unit emits a trigger signal in the form of a time quantity. The exact beginning of injection must take place at a particular crankshaft (angular) position. The specific angle from the time of the beginning of injection. For this reason, time quantities must be converted into angular sizes, and angular sizes into time quantities, by applying a rotational-speed value.
Furthermore, a method and device for controlling a solenoid-valve-controlled fuel pump are known from German Published Patent Application No. 40 04 107, which is also not prior art with respect to the present application. On the basis of the desired beginning of the delivery of fuel and the desired duration of the delivery, an electronic controlling system calculates the trigger instant and the shut-off instant for one or more solenoid valves. This calculation determines the switching times of the solenoid valves.
In the prior art, to determine the instantaneous rotational speed, the increment is evaluated before the trigger instants are calculated. The idea behind this procedure is that it is always the most current, instantaneous rotational speed that is relied upon in order to convert an angular size into a time quantity. Since the so-called starting increment for the time extrapolation must be exchanged depending upon the desired beginning of fuel delivery, the determined rotational-speed differential between two adjacent increments, between which the exchange is made, must not exceed a particular quantity. Since, however, the rotational speed fluctuates greatly from increment to increment, the result is that the injected fuel quantity is also subject to considerable fluctuations, causing poor running performance for the internal combustion engine.
Therefore, the object of the present invention is to improve the running performance of the internal combustion engine, and to minimize the fluctuations in the fuel metering.